I. Field of the Invention
The present invention relates to a microwave system of the type used in automotive vehicles and which achieves elevational scanning by frequency hopping.
II. Description of Related Art
Microwave systems using radio waves in the millimeter range have been allotted certain frequencies for automotive use. For example, the bandwidth of about 76.5 gigahertz-80 gigahertz has been allotted for automotive use by many countries. The bandwidth of allocation differs from country to country.
Many automotive systems utilize FMCW microwave systems with a radiator array for the antenna. The different elements in the radiator array are scanned in the horizontal direction using phase shifting for the various elements in the radiator array.
Previously, these FMCW automotive radar systems utilized the FMCW signal at a fixed frequency and the frequency modulation scanning at a fixed bandwidth. While this adequately provides horizontal scanning of the antenna, no previous attempt has been made to provide elevational scanning, i.e. scanning in the vertical direction. While such elevational scanning would be possible, for example, by mechanically tilting the antenna radiator array, the cost for doing so would be excessive with only a relatively small benefit. As such, these previously known automotive radar systems have not provided for any elevational scanning.